MRD as Biomarker for Response to Donor Lymphocyte Infusion after Allogeneic Hematopoietic Cell Transplantation in Patients with AML

Simple Summary Donor lymphocyte infusions (DLIs) are immune cells of the donor. They can potentially directly target leukemic cells. Thus, DLIs can be given to acute myeloid leukemia (AML) patients after allogeneic hematopoietic cell transplantation (alloHCT) in order to prevent or treat relapse. Measurable residual disease (MRD) describes very low levels of disease. Currently, it is still not well described how we can use MRD assessment for predicting response and outcome after DLI. This is a retrospective study looking at 76 AML patients receiving DLI treatment. MRD was evaluated prior to DLI treatment as well as 30 and 90 days after DLI. It was observed that within 90 days after DLI treatment, 73% of MRD+ patients converted to MRD-. Furthermore, MRD and remission status at the time of DLI were highly prognostic for the outcome (both for the relapse rate and also for relapse-free survival). Donor lymphocyte infusions (DLIs) can directly target leukemic cells through a graft-versus-leukemia effect and play a key role in the prevention and management of relapse after allogeneic hematopoietic cell transplantation (alloHCT). Predictors of response to DLIs are not well established. We evaluated measurable residual disease (MRD) before, 30 and 90 days after DLI treatment as biomarkers of response. MRD was assessed by next-generation sequencing in 76 DLI-treated acute myeloid leukemia patients. MRD status before DLI treatment was independently prognostic for event-free survival (EFS, p < 0.001) and overall survival (OS, p < 0.001). Within 90 days of DLI treatment, 73% of MRD+ patients converted to MRD- and 32% of patients without remission achieved remission. MRD status 90 days after DLI treatment was independently prognostic for the cumulative incidence of relapse (CIR, p = 0.011) and relapse-free survival (RFS, p = 0.001), but not for OS. To evaluate the role of DLI treatment in MRD- patients, 23 MRD- patients who received DLIs were compared with a control cohort of 68 MRD- patients not receiving DLIs. RFS (p = 0.23) and OS (p = 0.48) were similar between the two cohorts. In conclusion, MRD is prognostic before (EFS, OS) and after (CIR, RFS) DLI treatment and may help in the selection of patients who benefit most from DLIs.